Concentration of phosphate minerals



April 1955 w. M. HOUSTON EI'AL 2,706,558

CONCENTRATION OF PHOSPHATE MINERALS Filed Feb. 4, 1954 Phosphate Ore Feed Splitter Negative-ion Negative-ion Rougher Flotation Rougher Flotation Silicious Machine-Discharge to Waste Froth-Product Rougher Froth-Product Rougher Phosphate Concentrate Phosphate Concentrate 1 Mineral Acid Retarded Flotation Such as Middung J J Sulfuric Acld Machine-Discharge Agitation J Water Froth-Product High Grade Rinsing Phosphate Concentrate I Spent Reagents, (intermediate Product I) Slimes 8| Water to Waste Positive-ion Reagents Such as the Higher Aliphatic Amines Phosphate Concentrate (Intermediate Product 2) Silicious froth-Product to Waste F lnal High Grade Phosphate INVIdNTORS.

Concentrate WESLEY M. HOUSTON (Pmducm) l-IARWE M. BREATH/TZJR ATTORNEY United States Patent CONCENTRATION OF PHOSPHATE MINERALS Wesley M. Houston and Harvie W. Breathitt, Jr., Lakeland, Fla., assignors to Minerals & Chemicals Corporation of America, a corporation of Maryland Application February 4, 1954, Serial No. 408,140

3 Claims. (Cl. 209-166) The present invention relates to the concentration of phosphate minerals from their ores, and may be regarded as an improvement upon the method covered by the U. S. patent to Arthur Crago, 2,293,640, issued August 18, 1942.

The aforesaid Crago patent claims a method of concen trating phosphate minerals from their ores which comprises (first step) subjecting the ore, in an aqueous pulp, to a concentrating operation, by flotation with negativeion reagents, to separate a rougher concentrate of the phosphate values (in which is entrained silicious gangue) (second step) treating the said rougher phosphate concentrate with a mineral acid to remove the effect, insofar as flotation is concerned, of the negative-ion reagents used to produce said rougher concentrate; and then (thirdstep) subjecting the acid-treated rougher concentrate, in an aqueous pulp, to a concentrating positive-ion flotation operation, thereby producing a silicious froth-product which is discarded and a residue which is a high grade phosphate concentrate and the final product.

We have discovered a process, which is the present invention, for obtaining a high grade phosphate concentrate from phosphate ore, involving both negative-ion and positive-ion flotation operations as does the above outlined Crago method. As our description, which follows, and an appended flow sheet will clearly show, the process which is the present invention is similar to Cragos in two respects: (1) All of the feed ore is first sub ected to rougher flotation treatment and (2) the total rougher concentrate is further treated to separate it into high grade phosphate concentrate and silicious waste material. The novelty of our process, however, resides in the addition to the feed of the Crago process of a phosphate-rich middling obtained by retarded flotation, hereinafter defined, of a portion of the rougher phosphate concentrate. The advantage of our process is manifested in a marked reduction in positive-ion reagent consumption, even though about the same quantity of silica is removed from the rougher concentrate in our process as in Cragos.

The following outline of the steps (not a sequence of steps because some take place simultaneously) involved in putting the process of our invention into practice will serve to describe the particulars of said invention and also to give a good indication of its scope.

(1) Phosphate flotation feed is sub ected to negativeion froth flotation treatment, in an aqueous pulp, which produces therefrom rougher concentrate froth-product and silicious tailing which is sent to waste. Means for dividing the rougher concentrate either directly (after flotation) or indirectly (before flotation) are provided.

(2) Part of the rougher concentrate is sub ected to retarded flotation treatment which produces therefrom high grade phosphate concentrate froth product, (Intermediate Product 1 in the drawing) as part of the final product, and phosphate-rich middling machine-discharge. The retarded flotation can be carried out according to any of the methods of accomplishing same specified in U. S. Patent 2,661,842. By retarded flotation is meant flotation during which the normal floatability of the pulp 1S restricted in some manner to the end that the products emerge as described above.

(3) The other part of the rougher concentrate is dereagentized with a mineral acid (sulfuric acid is pre ferred) and then subjected to positive-ion froth flotation, in an aqueous pulp, to produce silicious froth-product, which can be sent to waste, and machine-discharge which 2,706,558 Patented Apr. 19, 1955 is high grade phosphate concentrate (Intermediate Product 2 in the drawing) and part of the final product (Product 3 in the drawing).

(4) The phosphate-rich middling from the retarded flotation treatment, or at least a substantial portion thereof, is directly combined with the feed from which is produced the rougher concentrate for the deoiling and sand flotation circuit. The point or points of addition of the middling can be anywhere between the point of entry of the feed ore and the point at which the feed enters the rougher cells. Thus, the entire middling can be fed to those rougher flotation cells feeding the deoiling and sand flotation circuit; or a portion of the middling can be thus directly fed and the remainder recycled to the rougher flotation cells feeding the retarded flotation circuit, either in the same ratio as, or in a different ratio from, that at which the new ore splits. It is to be understood that the percentage of the middling fed back is not critical but is restricted only by practical operating considerations. Thus, as little as about 20% of the middling could be fed back to the deoiling and sand flotation circuit, but such operation would seriously affect the capacity of the retarded flotation circuit.

In any situation where there is a split of the middling between the retarded float circuit and the deoiling and sand flotation (Crago) circuit, that part which goes back into the retarded float circuit will report again in the retarded middling and be split again and this procedure will be repeated until essentially all of the original middling has passed into the Crago circuit. For a flow sheet to represent a process within the scope of our invention, it must portray a flow of all or a substantial portion of the phosphate-rich middling from the retarded flotation circuit directly into the Crago circuit. Thus, a process in Which all of the middling is recirculated through rougher flotation and thence to retarded flotation again does not fall Within the definition of our invention.

As the above outline makes obvious, there are a number of specific ways to utilize our invention. We prefer the specific method shown in the attached flow sheet in which the incoming ore is split prior to rougher flotation, part going to a bank of rougher cells which are in the retarded float circuit and the remainder going to rougher cells which are part of the Crago circuit; the entire retarded middling being directly routed to the Crago roughers. Some of the more obvious variations of the process in which a substantial portion, but not all, of the retarded middling is combined with the feed to the Crago roughers are:

(1) Splitting the feed before rougher flotation and routing the middling to the feed ahead of the split.

2) Splitting the feed before rougher flotation, splitting the middling before adding it to new ore and routing part to the retarded circuit and the rest to the Crago circult.

(3) Splitting the rougher concentrate and routing the middling to the feed ahead of rougher flotation.

Following is the description of an exampleof putting our invention into practice according to our preferred method, for purposes of illustration.

Example I A 1,000 gram charge of plant flotation feed was conditioned with negative-ion reagents and subjected to froth flotation treatment, in an aqueous pulp, in a 1,000 gram laboTatory minerals separation airflow flotation machine. A froth-product which was a rougher phosphate concentrate and a silicious tailing were obtained.

The rougher concentrate was dewatered and then repulped in the flotation machine with water containing sulfuric acid in such proportion to give it a pH of 5.3. This pulp was agitated and aerated and a retarded froth-product which was a high grade phosphate concentrate (Intermediate Product 1 in the drawing) was removed, leaving a phosphate-rich middling in the flotation cell. More acid water like that used for the pulp dilution was employed to maintain the proper level in the cell during this flotation operation.

The aforesaid phosphate-rich middling was dewatered and its weight evaluated. Enough new feed was added to the middling to bring the weight of the mixture to 1,000 grams. The 1,000 gram charge was subjected to negative-ion flotation treatment, in an aqueous pulp, in a 1,000 gram laboratory minerals separation airflow flotation machine. A froth-product which was a rougher phosphate concentrate and a silicious tailing were obtained.

The rougher concentrate was agitated for about three minutes, in a pulp of approximately 50 per cent sol ds content, containing sulfuric acid, to deoil 1t. The solids were rinsed twice and then pulped 1n the flotatlon machine. Positive-ion reagents were added to the cell, the pulp was agitated for 15 seconds and then agitated and aerated to produce a silicious froth-product and a machine-discharge which was a high grade phosphate concentrate (Intermediate Product 2) making up the remainder of the finished product (the retarded froth-product being the other portion).

The reagent consumption was- FOR ROUGHER FLOTATION Po%nds lfPer 011 O Reagent Total Feed NaOH 9 Fuel Oil. 3 2 Tall Oil 0 7 FOR RETARDED FLOAT H2304 1.2

FOR DEOILING FOR SILICA FLOAT Kerosene 0. 15 Armac T 0.05

The metallurgical results are below.

Product Percent Percent Percent Wt. B. P. L sol. Recovery 1. Feed 100.0 26.8 100.0

RETARDED FLOAT CIRCUIT 2. Retarded float concentrate 8.2 75.6 3.0 22. 7 3. Rougher tailing 37.1 4.1 5. 6

SILICA FLOAT CIRCUIT 4. Silica float machine'discharge- 21.8 62.1 5. Silica float froth-product 1.5 1.4 6. Rougher tailing 31.4 8.2

OVERALL RESULTS 7. Combined concentrates (2 an 4) 30.0 71.2 2.3 84.8 8. Combined tailings (3 and 6)... 68. 5. 5 13. 8

A laboratory test was run using the earlier described Crago procedure on feed taken from the sample which supplied the feed for Example I. The quantities of reagents shown in the following table were consumed in this test.

Pounds Per Reagent Ton of Feed 4.0 Kerosene... 0. 33 Armac T O. 11

The metallurgical results are tabulated below.

A comparison of the reagent consumption of the Crago test with that of Example I shows that the Example I test used not as much H2804, less than half as much Armac T and less than half as much kerosene as the Crago one.

We claim:

1. A process for concentrating phosphate minerals from their ores which comprises the following operations: (1) subjecting suitably sized phosphate ore to froth flotation treatment, in an aqueous pulp, with negative-ion reagents, thereby producing rougher concentrate material (froth product) and silicious waste material (tailing); (2) subjecting the rougher concentrate from part of the said ore to retarded froth flotation treatment in an aqueous pulp and removing, as part of the final product, a concentrate froth-product having a low insoluble content and a phosphate-rich middling residue; (3) subjecting the rougher concentrate from the remaining part of said ore, in an aqueous pulp, to treatment with a mineral acid followed by rinsing with water, thus removing from said rougher concentrate substantially all of the adhering negative-ion reagents; (4) subjecting said acid-treated and rinsed rougher concentrate, in an aqueous pulp, to frothflotation treatment with positive-ion reagents, thereby producing a froth-product composed mostly of silicious gangue which is discarded, and a residue which is a high grade phosphate concentrate which can be combined with the high grade phosphate concentrate from the previously mentioned (2) retarded floats; (5) combining at least a substantial portion of the phosphate-rich middling residue from the retarded flotation operation (2) directly with that part of the ore from which is subsequently produced the rougher concentrate for the previously mentioned (4) positive-ion flotation treatment.

2. A process for concentrating phosphate minerals from their ores comprising the following operations: (1) Dividing the ore into two separate parts and subjecting each art, in an aqueous pulp, to negative-ion froth flotation treatment, thereby producing two rougher concentrate froth-products of phosphate values mixed with some silicious gangue, and two silicious tailing products which are sent to waste; (2) subjecting one of said rougher concentrates, in an aqueous pulp, to retarded froth flotation treatment and removing, as a part of the final product, a phosphate concentrate froth-product having a low insoluble content, and a phosphate-rich middling residue which is directly combined with that part of the feed from which is produced the other said rougher phosphate concentrate; (3) subjecting the other said rougher phosphate concentrate, in an aqueous pulp, to treatment with a mineral acid followed by rinsing with water, thereby removing from said rougher concentrate substantially all of the adhering negative-ion reagents; and (4) subjecting said acid treated and rinsed rougher concentrate in an aqueous pulp to a froth-flotation treatment with positiveion reagents, thereby producing a froth product mostly composed of silicious gangue which is discarded, and a residue which is a high grade phosphate concentrate and can be combined with the previously mentioned phosphate concentrate from step (2); thereby producing a final high grade phosphate concentrate containing a high proportion of the phosphate in the ore.

3. The process of claim 1 wherein the phosphate-rich middling from the retarded float is combined with the feed ore ahead of where said feed ore is divided into the two separate parts.

References Cited in the file of this patent UNITED STATES PATENTS 2,293,640 Crago Aug. 18, 1942 2,661,842 Duke et al Dec. 8, 1953 2,676,705 Duke et a1. Apr. 27, 1954 

1. A PROCESS FOR CONCENTRATING PHOSPHATE MINERALS FROM THEIR ORES WHICH COMPRISES THE FOLLOWING OPERATIONS: (I) SUBJECTING SUITABLY SIZED PHOSPHATE ORE TO FROTH FLOATATION TREATMENT, IN AN AQUEOUS PULP, WITH NEGATIVE-ION REAGENTS, THEREBY PRODUCING ROUGHER CONCENTRATE MATERIAL (FROTHPRODUCT) AND SILICIOUS WASTE MATERIAL (TAILING); (2) SUBJECTING THE ROUGHER CONCENTRATE FROM PART OF THE SAID ORE TO RETARDED FROTH FLOTATION TREATMENT IN AN AQUEOUS PULP AND REMOVING, AS PART OF THE FINAL PRODUCT, A CONCENTRATE FROTH-PRODUCT HAVING A LOW INSOLUBLE CONTENT AND A PHOSPHATE-RICH MIDDLING RESIDUE; (3) SUBJECTING THE ROUGHER CONCENTRATE FROM THE REMAINING PART OF SAID ORE, IN AN AQUEOUS PULP, TO TREATMENT WITH A MINERAL ACID FOLLOWED BY RINSING WITH WATER, THUS REMOVING FROM SAID ROUGHER CONCENTRATE SUBSTANTIALLY ALL OF THE ADHERING NEGATIVE-ION REAGENTS: (4) SUBJECTING SAID ACID-TREATED AND RINSED ROUGHER CONCENTRATE, IN AN AQUEOUS PULP, TO FROTHFLOTATION TREATMENT WITH POSITIVE-ION REAGENTS, THEREBY PRODUCING A FROTH-PRODUCT COMPOSED MOSTLY OF SILICIOUS GANGUE WHICH IS DISCARDED, AND A RESIDUE WHICH IS A HIGH GRADE PHOSPHATE CONCENTRATE WHICH CAN BE COMBINED WITH THE HIGH GRADE PHOSPHATE CONCENTRATE FROM THE PREVIOUSLY MENTIONED (2) RETARDED FLOATS: (5) COMBINING AT LEAST A SUBSTANIAL PORTION OF THE PHOSPHATE-RICH MIDDLING RESIDUE FROM THE RETARDED FLOTATION OPERATION (2)-DIRECTLY WITH THAT PART OF THE ORE FROM WHICH IS SUBSEQUENTLY PRODUCED THE ROUGHER CONCENTRATE FOR THE PREVIOUSLY MENTIONED (4) POSITIVE-ION FLOTATION TREATMENT. 